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Visual Cortex + Benjolin
MUFF WIGGLER Forum Index -> Video Synthesis  
Author Visual Cortex + Benjolin

noisejockey

I'm super scared of posting here at all, as I've got off-and-on experience in pro video and motion design for over 25 years and I'm a modular nut and I need another money pit like another hole in the head. But I'm a video synth newb with excess audio oscillators, which leads me to my question:

I've got a Eurorack Benjolin that needs a second life. With attenuators, would that make an interesting companion, rather than two prismatic rays, to a Visual Cortex + Bridge + (Passage? Doorway? Staircase?) starter system? With its filtered outputs (already very attenuated) and Rungler output and two oscillators, seems like a pretty flexible complex oscillator for video shenanigans...but curious if anyone has specific thoughts there.

I'm most keen to keep all output utterly monochromatic, and I have non-modular upscalers to take it out to the displays I have in mind.

Meh? Blech? Woohoo?


evolve

You are going to find that audio oscillators are very different than video oscillators. What I would suggest is, getting the visual cortex, then trying some of your audio modules with it.


james_keith

Benjolin is definitely a power tool for oscillographics. I've been working with one set up with a vectrex monitor modified to accept x,y,z inputs. I don't have video on hand, but here is some stuff someone else has recorded:

https://vimeo.com/137634787


vonkhades

noisejockey wrote:
I'm super scared of posting here at all, as I've got off-and-on experience in pro video and motion design for over 25 years and I'm a modular nut and I need another money pit like another hole in the head. But I'm a video synth newb with excess audio oscillators, which leads me to my question:

I've got a Eurorack Benjolin that needs a second life. With attenuators, would that make an interesting companion, rather than two prismatic rays, to a Visual Cortex + Bridge + (Passage? Doorway? Staircase?) starter system? With its filtered outputs (already very attenuated) and Rungler output and two oscillators, seems like a pretty flexible complex oscillator for video shenanigans...but curious if anyone has specific thoughts there.

I'm most keen to keep all output utterly monochromatic, and I have non-modular upscalers to take it out to the displays I have in mind.

Meh? Blech? Woohoo?


AFAIK you will still need at least one video oscillator, because audio oscillator dont go fast enough (MHz) to be used to paint vertically... So if you use audio oscillartor you will only get horizontal bars and thats it... you will need to mix vertical range stuff with horizontal to make interesting stuf..

Im starting video synth too (like 3 months ago) and found this super usefull

https://www.lzxindustries.net/system/using-audio-synths-for-video/

Also if you are on budget consider going DIY with LZX Cadets.


schwittersplayspop

Having read that you need a special VCO for horizontal, here:

https://www.lzxindustries.net/system/using-audio-synths-for-video/

where the Prismatic Ray is recommended, I'm slightly confused as to the system recommendations for systems with audio Eurorack, which all ignore the Prismatic Ray (Starter System 2 and Basic System 2):

https://www.lzxindustries.net/system/system-build-examples/

Also, most of those systems (until the 12U, well beyond what I would want to do) ignore the newer Sensory Translator module, which seems designed for audio integration, which also seems confusing.

Any thoughts on these points from more experienced video people? Thanks!


Dirty_Bill

Noisejockey, if you want to see what it will do (and I'm knd of curous too) send me a message and we can hook it up and take a look!


hinotori

I'd not seen that page on the LZX site before, although it is correct it could lead to a little confusion for some regarding the horizontal vs vertical, as it doesn't have any example images of what might be seen onscreen.

When demoing direct video synthesis to people who have a knowledge of audio there are a couple of things that help keep things easy to understand. Apologies in advance if you already know all this, as there are examples of this online, youtube etc:

Low low frequency oscillations (saw or sine in this case) will produce a slow fading in and out of a single colour across the whole screen.

As the frequency is increased we start to see the oscillator form horizontal lines on the screen. So where the LZX page says "Signals between frame rate (~30 Hz) and the horizontal sync rate (~15KHz) are in the vertical frequency domain. " it is important to remember that it is talking about the video signal and sync/frame rates but that in this frequency range we are seeing HORIZONTAL lines. This is the frequency range that most audio oscillators occupy, although some can go lower and also some higher, ill talk about this a little later. The lower frequencies in this range will produce a single horizontal line and the number of lines increase as the frequency rises.

As we continue to increase the frequency we enter what the LZX page calls the horizontal frequency domain. "Signals above the horizontal sync rate (~15 KHz) and video bandwidth (~6MHz) are in the horizontal frequency domain."
So, as we reach the limit of the number of horizontal lines on screen the lines twist and start to form vertical lines, again starting with one vertical line at the lower end of this frequency range and then increasing the number of vertical lines as the frequency increases. Until eventually we kind of get a visual noise with most oscillators as the sync becomes unstable, though i've not tested this with the LZX oscillators as my LZX system doesn't include any.

A very important this to note when we try to visualise the correspondence between an audio tone increasing in frequency and an increasing visual "tone" is that although the audio tone steadily increases in a linear/log trajectory the visual "tone"/"pattern" does not, the lines are only stable when they are synced or are exact multiples of the vertical or horizontal sync signals. Between these values they cycle left and right or up and down as they approach their synced comfort zones. So, as the eye hears a straight progression from low to high the eye sees a phasing in and out of time of the visual pattern is it goes in and out of sync with the vertical and horizontal sync signals.

This leads us to the importance of sync when using audio oscillators to create direct video synthesis lines and patterns.

So, when selecting audio oscillators to use with a video system we have to consider the upper and lower limits to their frequency range, their wave shapes (square/pulse waves just cause a flashing screen at low frequencies, and solid monotone bars with no gradiation at higher frequencies), their ability to sync and last but not least their FM inputs (lin/exp) as along with summing and multiplying oscillators together this is where a lot of the magic happens when creating more complex or visually interesting patterns and shapes.

Some audio oscillators, and fully resonant filters producing sine waves, can be pushed into producing high numbers of horizontal lines across the screen but few can produce vertical lines, and this, along with their stability and the fact that you need far finer and more delicate control of the frequency as it gets into higher range is why the LZX oscillators are a great solid and precise option for any video synthesis system.

There are other threads here that discuss what audio modules are useful for video synthesis including and beyond just oscillators, but a great option for anyone into DIY (or with a kind friend who is) are the Thomas Henry 555VCO oscillators. These can be easily modded to cover the entire useful frequency range for video synthesis, from low, to horizontal lines up to vertical lines. It is worth noting that all signals will have to be attenuated, using an LZX voltage bridge or similar, though the weak sin out on the TH is a bonus here as it is already slightly attenuated down in comparison to the other waveforms output by the module. The other thing is that to get it to sync the sync out signals from the LZX visual cortex or similar will have to be amplified before running into the 555VCO. Another thing that is important to note is that if you are using audio modules to attenuate the signals then they may have to be modified. They will need their opamps replacing with higher frequency / higher bandwidth opamps, in several cases alternatives can be found with the same pin outs if you check datasheets and are simple a matter of dropping them in. But this is not always the case, im currently trying to find a good high bandwidth alternative to the LM137000 so I can mod wavefolders for video rate but am yet to find one. There are several amplifiers, mixers, wavefolders, logic and oscillators that are designed for audio that although they will work as a part of a video synthesis system can be modded for increased frequency/bandwidth to avoid them filtering out higher frequencies, which in the case of video signals is the edges and the detail in the image.

I hope some of that helps.


ebbflo

hinotori wrote:
a great option for anyone into DIY (or with a kind friend who is) are the Thomas Henry 555VCO oscillators. These can be easily modded to cover the entire useful frequency range for video synthesis, from low, to horizontal lines up to vertical lines.


Great tip, thanks!
How "smooth" is the sine on the TH? or how smooth have you been able to get them.


spacenoodle

Would sending audio oscillators through Staircase make them function well enough for video? Anyone here tried Staircase yet?


destroythings

vonkhades wrote:
noisejockey wrote:
I'm super scared of posting here at all, as I've got off-and-on experience in pro video and motion design for over 25 years and I'm a modular nut and I need another money pit like another hole in the head. But I'm a video synth newb with excess audio oscillators, which leads me to my question:

I've got a Eurorack Benjolin that needs a second life. With attenuators, would that make an interesting companion, rather than two prismatic rays, to a Visual Cortex + Bridge + (Passage? Doorway? Staircase?) starter system? With its filtered outputs (already very attenuated) and Rungler output and two oscillators, seems like a pretty flexible complex oscillator for video shenanigans...but curious if anyone has specific thoughts there.

I'm most keen to keep all output utterly monochromatic, and I have non-modular upscalers to take it out to the displays I have in mind.

Meh? Blech? Woohoo?


AFAIK you will still need at least one video oscillator, because audio oscillator dont go fast enough (MHz) to be used to paint vertically... So if you use audio oscillartor you will only get horizontal bars and thats it... you will need to mix vertical range stuff with horizontal to make interesting stuf..

Im starting video synth too (like 3 months ago) and found this super usefull

https://www.lzxindustries.net/system/using-audio-synths-for-video/

Also if you are on budget consider going DIY with LZX Cadets.


The Inteljiel Dixie II+ is a great cheap audio module than can run in LFO or VCO mode and has a octave switch up to +8 and it can paint vertically which not many audio modules can handles. Its also ha multiple wave shape outputs so works really well as a cheap video oscillator.


schwittersplayspop

Thanks for the detailed description, hinotori! I think I'll be coming back to your post again and again. Lots to digest, so much appreciated!

On the subject of high-frequency audio oscillators, I do have a Denum (which rated highest of the Eurorack modules considered in this survey: http://pugix.com/synth/maximum-high/) to play with. It's a difficult oscillator to operate, but could be promising for video from the sounds of it.


Dirty_Bill

schwittersplayspop wrote:

On the subject of high-frequency audio oscillators, I do have a Denum (which rated highest of the Eurorack modules considered in this survey: http://pugix.com/synth/maximum-high/) to play with. It's a difficult oscillator to operate, but could be promising for video from the sounds of it.


Off topic - I could get the Ultrasounds of my Plumbutter to run at video rates, fairly stable but no real sync. Please share any experiments!


nangu

Here's some video. Most of these were done with just a Benjolin (the Epoch version), Visual Cortex, and a Thonk AT-AT-AT attenuator.

Some of the later ones may have Staircase on them- I don't remember whether I quit recording before or after I started using Staircase. I didn't manage to make Benjolin go vertical with it, so perhaps I didn't record any Staircase..




















Nino

wow thanks a lot for posting this SlayerBadger!


ju4n

schwittersplayspop wrote:
Thanks for the detailed description, hinotori! I think I'll be coming back to your post again and again. Lots to digest, so much appreciated!

On the subject of high-frequency audio oscillators, I do have a Denum (which rated highest of the Eurorack modules considered in this survey: http://pugix.com/synth/maximum-high/) to play with. It's a difficult oscillator to operate, but could be promising for video from the sounds of it.


more on this probably does belong in the dedicated audio modules stickied thread, but...

Regarding the frequency survey, I think there can be more to consider when experimenting with audio oscillators. some have better/worse response to sync, more or less cv input controls, tuning accuracy for dialing in really specific frequencies, not to mention a method for increasing the range beyond the frequency controls of the module is to send an offset voltage to one of the FM inputs.

for instance i had an original dixie in my video system that worked pretty well. decent response to sync at specific frequencies and i could get up to something like,3-4 vertical bars with a +5v offset past the maximum tune setting.

on a demo system in a synth shop i tried an AFG into a VC and i seem to remember it had a more limited range and super difficult to get anything beyond jittery strobing chaotic pulsing.


hinotori

nice to see those clips! thanks for sharing

Its been a while since I tried this but the sines from the TH 555 were nice, I didn't check on a scope though. but aside from needing to scale the 5v down to 1v etc they seem to me to be the most affordable video oscillator, though I know DIY isn't for everyone.

Lots of this info probably does belong on the dedicated audio modules in video rigs thread but no harm in repeating things when relevant.

If anyone is in to their DIY I can recommend modifying Lunetta circuits for video, its a cheap and easy route for getting nice video oscillators. I might be wrong but I think that the 3 oscs in the 3trins are based on similar chips/designs. Just do a google image search for Lunetta VCO schematic or something similar and breadboard it, then mess with the cap and resistor values that alter the frequency until you find the sweet spot. A friend and I managed to build a nice bank of oscillators that all happily synced to the LZX sync gen / cortex, as well as comparators (key gens) and other bits. It was quite a while ago but we may resurrect the project and I'll post some images if I find them. (Getting off topic i know)


hinotori

ju4n wrote:

Regarding the frequency survey, I think there can be more to consider when experimenting with audio oscillators. some have better/worse response to sync, more or less cv input controls, tuning accuracy for dialing in really specific frequencies, not to mention a method for increasing the range beyond the frequency controls of the module is to send an offset voltage to one of the FM inputs.


+1 for all this info, absolutely true, and the only real big issue with a modded TH 555 is getting the tuning accuracy at higher frequencies / vertical bars. This is why its well worth having an LZX osc, I am opting for a few of the diy cadet oscs for vertical bar duties.

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